The present invention relates to mechanical filter presses for extracting water from industrial or municipal sludges and, more specifically, to a continuous-process sludge dewatering system including means for moving the sludge through a succession of cavities of decreasing cross section.
Sludges, as the term is used herein, are mixtures of one or more liquids and solids wherein the liquid is entrapped, sometimes being molecularly bound to the solids, and is difficult to remove by conventional means. Gravity settling is time consuming and often only marginally effective. Some sludges may be separable into solid and liquid phases by chemical treatment, or by freezing and thawing, but such treatment is often expensive and depends highly upon the chemical composition of the sludge being treated. Air-drying is ineffective since a crust forms at the surface, inhibiting further evaporation, and drying by application of non-solar heat is economically unfeasible.
Disposal of water-laden sludges presents both economic and environmental problems of ever-increasing magnitude. Since it is not uncommon for sludge to have a liquid content in excess of 90%, the disposal of separated phases is vastly simpler than that of untreated sludge. In many cases, one or both of the liquid and solid phases may be recycled or otherwise usefully employed after separation. Thus, there remains a need for sludge dewatering means which are both efficient in operation and economically justifiable, and it is the principal object of the present invention to provide such a system.
More specifically, the object of the invention is to provide a continuous-process sludge dewatering system employing a mechanical press wherein the sludge is passed through a succession of cavities of sequentially reduced cross section as liquid is removed.
Other objects will in part be obvious and will in part appear hereinafter.